Barrier technology - Wetting behaviour - Rough and porous surfaces

3 important questions on Barrier technology - Wetting behaviour - Rough and porous surfaces

Why are rough surfaces more difficult to coat?

The ends of the corrugations may still stick out of the coating. Since the product is much more permeable to the permeant than the coating material, this will lead to defects in the coating, which will destroy any barrier functions.
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Rough surfaces are difficult to coat, how can that be improved?

  • By adding a second coating layer of the same coating.
  • By application of surfactants, the contact angle can be reduced sufficiently (below 90 degrees)
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How can porous surfaces be useful in the formation of a coating?

When using a dispersions or emulsion, the solvent is drained into the pores. The emulsion or dispersion droplets that remain at the surface are able to form a dense layer covering the product. This also reduces the need for a drying step, as the moisture disappears into the product.

The concentration of moisture in the sublayer will increase somewhat, which may have negative effects on its quality.
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